Conventionally, a known thermal-type airflow measuring device is equipped to an air intake passage of an engine. The airflow measuring device is configured to draw a part of air, which flows through the air intake passage, and to cause heat transfer with the drawn air, thereby to measure a flow quantity of air drawn into the engine.
Patent Document 1 discloses an airflow measuring device equipped with an intake-air temperature sensor and a moisture sensor in addition to a flow sensor.
It is noted that, the airflow measuring device according to Patent Document 1 has two different passages including one passage, which is equipped with the flow sensor, and the other passage, which is equipped with the moisture sensor. Therefore, the configuration of Patent Document 1 may require connection forms between sensors and an external device, which are significantly different among sensors. In addition, the configuration of Patent Document 1 may require complicated arrangement of wirings and complicated mounting process of the sensors. Furthermore, the configuration of Patent Document 1 may require large modification in configuration of the housing of the airflow measuring device and large modification in a mounting process of the sensors, in a case where the number of a sensor other than the flow sensor and a type of the sensor are selectively modified for each product.
(Patent Document 1)
Japanese Patent Gazette No. 5178388